A new approach to chromeno[4,3-b]pyridine: Synthesis, X-ray, spectral investigations, hirshfeld surface analysis, and computational studies

Abstract

The structural motif of chromeno[4,3-b]pyridine can be found in a wide variety of pharmaceuticals and bioactive compounds. In this study, we have synthesized 2-(4,5-di-p-tolyl-5H-chromeno[4,3-b]pyridin-2-yl)phenol utilizing microwave radiation as an eco-friendly procedure upon the reaction of 2′-hydroxy-4-methylchalcone with urea under basic conditions. The obtained compound was confirmed using spectroscopic analysis, including FT-IR, UV–visible, 1H NMR, 13C NMR, mass spectroscopy, and X-ray crystallography. Moreover, the crystal structure of the chromeno[4,3-b]pyridine derivative exhibited a monoclinic system and Pc space group. Theoretical calculations were used as a comparative study of the X-ray crystal structure of this chromenopyridine using the B3LYP and HF/6–311(G) basis set and experimental bond length and angles, which showed that the HF method was more accurate than the DFT method. Furthermore, the calculated NMR, FT-IR, and UV–vis spectra obtained for the chromeno[4,3-b]pyridine derivative were in good agreement with the experimental data. In addition, the Mulliken charges, MEP, and HOMO-LUMO energy gap of this chromenopyridine were theoretically calculated. The Hirshfeld surface analysis showed the most important interactions formed between the molecules in the crystal.